A casting method for the three-dimensional analysis of the intraprism structural pores in vertisols

• Published in: European journal of soil science 1998-06, Vol.49 (2), p.187-196
• Main Authors: CABIDOCHE, Y.-M, GUILLAUME, P
• Format: Article
• Language: English
• Subjects: Agricultural sciences; Agronomy. Soil science and plant productions; Biological and medical sciences; Earth sciences; Earth, ocean, space; Exact sciences and technology; Fundamental and applied biological sciences. Psychology; Life Sciences; Physical properties; Physics, chemistry, biochemistry and biology of agricultural and forest soils; Soil science; Soil study; Soils; Structure, texture, density, mechanical behavior. Heat and gas exchanges; Surficial geology
• ISSN: 1351-0754; 1365-2389
• DOI: 10.1046/j.1365-2389.1998.00162.x

The structural voids in vertisols contain easily available water for plants and their volume can be calculated from the shrinkage curve. Access by plants to that water depends also on the geometric arrangement of the pores so that the water can flow through them. We have devised a method for studying the structural porosity by casting the pores in resin. The intraprism pore space of wet soil clods is impregnated with a UV fluorescent polyester resin under vacuum. When this has set we use the swelling properties of the clay to separate the clay matrix from the resin. A cast so obtained is the real three‐dimensional solid reproduction of the structural porosity. This representation of the pore system is easier to study than results from computerized reconstitution of the three‐dimensional space from two‐dimensional images of soil in thin sections. Channels, packing pores and planar voids can be observed directly in three dimensions as the method saves the integrity and continuity of pores as small as 10 μm in diameter. The geometry of the cast shapes agrees with the interpretation of shrinkage and moisture characteristic curves. The method offers direct qualitative observation of pore organization and volume measurements of the intraprism structural porosity in vertisols.